- A0
- B1
- C2
- D-1
Step-by-Step Solution
sin means °, so cos . (This equals cos = cos 90° = 0.)
Answer: A) 0
If sin , what is the value of 3 cos coA? (A is acute.)
Class 10Introduction to TrigonometryTrigonometry
Key idea: Standard angle values (must memorise)
| θ | 0° | 30° | 45° | 60° | 90° |
|---|---|---|---|---|---|
| sin θ | 0 | 1/2 | √2/2 | √3/2 | 1 |
| cos θ | 1 | √3/2 | √2/2 | 1/2 | 0 |
| tan θ | 0 | 1/√3 | 1 | √3 | undefined |
**Memory pattern for sin**: 0/2, 1/2, √2/2, √3/2, √4/2 = 0, 1/2, √2/2, √3/2, 1. (Take square roots of 0,1,2,3,4 over 2.)
**For cos**: same pattern but in REVERSE order.
**For tan**: tan = sin/cos.
These values appear in every standardised assessment. Memorise the table cold.
|---|---|---|---|---|---|
| sin θ | 0 | 1/2 | √2/2 | √3/2 | 1 |
| cos θ | 1 | √3/2 | √2/2 | 1/2 | 0 |
| tan θ | 0 | 1/√3 | 1 | √3 | undefined |
**Memory pattern for sin**: 0/2, 1/2, √2/2, √3/2, √4/2 = 0, 1/2, √2/2, √3/2, 1. (Take square roots of 0,1,2,3,4 over 2.)
**For cos**: same pattern but in REVERSE order.
**For tan**: tan = sin/cos.
These values appear in every standardised assessment. Memorise the table cold.
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More Class 10 Introduction to Trigonometry practice
The maximum value that sin θ can take is:Assertion (A): tan(90° − θ) = cot θ. Reason (R): In a right triangle the two acute…In right triangle PQR, right-angled at Q, PQ = 9 cm, QR = 12 cm and PR = 15 cm. A…In right triangle ABC, right-angled at C, AC = 9 cm and BC = 40 cm. Find cot A.In right triangle ABC, right-angled at B, AB = 5 cm and BC = 12 cm. Find sec C.